drm/i915: buddy allocator

Simple buddy allocator. We want to allocate properly aligned
power-of-two blocks to promote usage of huge-pages for the GTT, so 64K,
2M and possibly even 1G. While we do support allocating stuff at a
specific offset, it is more intended for preallocating portions of the
address space, say for an initial framebuffer, for other uses drm_mm is
probably a much better fit. Anyway, hopefully this can all be thrown
away if we eventually move to having the core MM manage device memory.

Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20190809202926.14545-2-matthew.auld@intel.com

7 files changed, 1282 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile
index 3b1fde735c91..a3f6f455b7ff 100644
--- a/drivers/gpu/drm/i915/Makefile
+++ b/drivers/gpu/drm/i915/Makefile
@@ -127,6 +127,7 @@ gem-y += \
 i915-y += \
 	  $(gem-y) \
 	  i915_active.o \
+	  i915_buddy.o \
 	  i915_cmd_parser.o \
 	  i915_gem_evict.o \
 	  i915_gem_fence_reg.o \
diff --git a/drivers/gpu/drm/i915/i915_buddy.c b/drivers/gpu/drm/i915/i915_buddy.c
new file mode 100644
index 000000000000..b679ab6fd889
--- /dev/null
+++ b/drivers/gpu/drm/i915/i915_buddy.c
@@ -0,0 +1,431 @@
+// SPDX-License-Identifier: MIT
+/*
+ * Copyright © 2019 Intel Corporation
+ */
+
+#include <linux/slab.h>
+
+#include "i915_buddy.h"
+
+#include "i915_gem.h"
+#include "i915_globals.h"
+#include "i915_utils.h"
+
+static struct i915_global_block {
+	struct i915_global base;
+	struct kmem_cache *slab_blocks;
+} global;
+
+static void i915_global_buddy_shrink(void)
+{
+	kmem_cache_shrink(global.slab_blocks);
+}
+
+static void i915_global_buddy_exit(void)
+{
+	kmem_cache_destroy(global.slab_blocks);
+}
+
+static struct i915_global_block global = { {
+	.shrink = i915_global_buddy_shrink,
+	.exit = i915_global_buddy_exit,
+} };
+
+int __init i915_global_buddy_init(void)
+{
+	global.slab_blocks = KMEM_CACHE(i915_buddy_block, SLAB_HWCACHE_ALIGN);
+	if (!global.slab_blocks)
+		return -ENOMEM;
+
+	return 0;
+}
+
+static struct i915_buddy_block *i915_block_alloc(struct i915_buddy_block *parent,
+						 unsigned int order,
+						 u64 offset)
+{
+	struct i915_buddy_block *block;
+
+	block = kmem_cache_zalloc(global.slab_blocks, GFP_KERNEL);
+	if (!block)
+		return NULL;
+
+	block->header = offset;
+	block->header |= order;
+	block->parent = parent;
+
+	return block;
+}
+
+static void i915_block_free(struct i915_buddy_block *block)
+{
+	kmem_cache_free(global.slab_blocks, block);
+}
+
+static void mark_allocated(struct i915_buddy_block *block)
+{
+	block->header &= ~I915_BUDDY_HEADER_STATE;
+	block->header |= I915_BUDDY_ALLOCATED;
+
+	list_del(&block->link);
+}
+
+static void mark_free(struct i915_buddy_mm *mm,
+		      struct i915_buddy_block *block)
+{
+	block->header &= ~I915_BUDDY_HEADER_STATE;
+	block->header |= I915_BUDDY_FREE;
+
+	list_add(&block->link,
+		 &mm->free_list[i915_buddy_block_order(block)]);
+}
+
+static void mark_split(struct i915_buddy_block *block)
+{
+	block->header &= ~I915_BUDDY_HEADER_STATE;
+	block->header |= I915_BUDDY_SPLIT;
+
+	list_del(&block->link);
+}
+
+int i915_buddy_init(struct i915_buddy_mm *mm, u64 size, u64 chunk_size)
+{
+	unsigned int i;
+	u64 offset;
+
+	if (size < chunk_size)
+		return -EINVAL;
+
+	if (chunk_size < PAGE_SIZE)
+		return -EINVAL;
+
+	if (!is_power_of_2(chunk_size))
+		return -EINVAL;
+
+	size = round_down(size, chunk_size);
+
+	mm->size = size;
+	mm->chunk_size = chunk_size;
+	mm->max_order = ilog2(size) - ilog2(chunk_size);
+
+	GEM_BUG_ON(mm->max_order > I915_BUDDY_MAX_ORDER);
+
+	mm->free_list = kmalloc_array(mm->max_order + 1,
+				      sizeof(struct list_head),
+				      GFP_KERNEL);
+	if (!mm->free_list)
+		return -ENOMEM;
+
+	for (i = 0; i <= mm->max_order; ++i)
+		INIT_LIST_HEAD(&mm->free_list[i]);
+
+	mm->n_roots = hweight64(size);
+
+	mm->roots = kmalloc_array(mm->n_roots,
+				  sizeof(struct i915_buddy_block *),
+				  GFP_KERNEL);
+	if (!mm->roots)
+		goto out_free_list;
+
+	offset = 0;
+	i = 0;
+
+	/*
+	 * Split into power-of-two blocks, in case we are given a size that is
+	 * not itself a power-of-two.
+	 */
+	do {
+		struct i915_buddy_block *root;
+		unsigned int order;
+		u64 root_size;
+
+		root_size = rounddown_pow_of_two(size);
+		order = ilog2(root_size) - ilog2(chunk_size);
+
+		root = i915_block_alloc(NULL, order, offset);
+		if (!root)
+			goto out_free_roots;
+
+		mark_free(mm, root);
+
+		GEM_BUG_ON(i > mm->max_order);
+		GEM_BUG_ON(i915_buddy_block_size(mm, root) < chunk_size);
+
+		mm->roots[i] = root;
+
+		offset += root_size;
+		size -= root_size;
+		i++;
+	} while (size);
+
+	return 0;
+
+out_free_roots:
+	while (i--)
+		i915_block_free(mm->roots[i]);
+	kfree(mm->roots);
+out_free_list:
+	kfree(mm->free_list);
+	return -ENOMEM;
+}
+
+void i915_buddy_fini(struct i915_buddy_mm *mm)
+{
+	int err = 0;
+	int i;
+
+	for (i = 0; i < mm->n_roots; ++i) {
+		if (!i915_buddy_block_is_free(mm->roots[i])) {
+			err = -EBUSY;
+			continue;
+		}
+
+		i915_block_free(mm->roots[i]);
+	}
+
+	kfree(mm->roots);
+	kfree(mm->free_list);
+}
+
+static int split_block(struct i915_buddy_mm *mm,
+		       struct i915_buddy_block *block)
+{
+	unsigned int block_order = i915_buddy_block_order(block) - 1;
+	u64 offset = i915_buddy_block_offset(block);
+
+	GEM_BUG_ON(!i915_buddy_block_is_free(block));
+	GEM_BUG_ON(!i915_buddy_block_order(block));
+
+	block->left = i915_block_alloc(block, block_order, offset);
+	if (!block->left)
+		return -ENOMEM;
+
+	block->right = i915_block_alloc(block, block_order,
+					offset + (mm->chunk_size << block_order));
+	if (!block->right) {
+		i915_block_free(block->left);
+		return -ENOMEM;
+	}
+
+	mark_free(mm, block->left);
+	mark_free(mm, block->right);
+
+	mark_split(block);
+
+	return 0;
+}
+
+static struct i915_buddy_block *
+get_buddy(struct i915_buddy_block *block)
+{
+	struct i915_buddy_block *parent;
+
+	parent = block->parent;
+	if (!parent)
+		return NULL;
+
+	if (parent->left == block)
+		return parent->right;
+
+	return parent->left;
+}
+
+static void __i915_buddy_free(struct i915_buddy_mm *mm,
+			      struct i915_buddy_block *block)
+{
+	struct i915_buddy_block *parent;
+
+	while ((parent = block->parent)) {
+		struct i915_buddy_block *buddy;
+
+		buddy = get_buddy(block);
+
+		if (!i915_buddy_block_is_free(buddy))
+			break;
+
+		list_del(&buddy->link);
+
+		i915_block_free(block);
+		i915_block_free(buddy);
+
+		block = parent;
+	}
+
+	mark_free(mm, block);
+}
+
+void i915_buddy_free(struct i915_buddy_mm *mm,
+		     struct i915_buddy_block *block)
+{
+	GEM_BUG_ON(!i915_buddy_block_is_allocated(block));
+	__i915_buddy_free(mm, block);
+}
+
+void i915_buddy_free_list(struct i915_buddy_mm *mm, struct list_head *objects)
+{
+	struct i915_buddy_block *block, *on;
+
+	list_for_each_entry_safe(block, on, objects, link)
+		i915_buddy_free(mm, block);
+	INIT_LIST_HEAD(objects);
+}
+
+/*
+ * Allocate power-of-two block. The order value here translates to:
+ *
+ *   0 = 2^0 * mm->chunk_size
+ *   1 = 2^1 * mm->chunk_size
+ *   2 = 2^2 * mm->chunk_size
+ *   ...
+ */
+struct i915_buddy_block *
+i915_buddy_alloc(struct i915_buddy_mm *mm, unsigned int order)
+{
+	struct i915_buddy_block *block = NULL;
+	unsigned int i;
+	int err;
+
+	for (i = order; i <= mm->max_order; ++i) {
+		block = list_first_entry_or_null(&mm->free_list[i],
+						 struct i915_buddy_block,
+						 link);
+		if (block)
+			break;
+	}
+
+	if (!block)
+		return ERR_PTR(-ENOSPC);
+
+	GEM_BUG_ON(!i915_buddy_block_is_free(block));
+
+	while (i != order) {
+		err = split_block(mm, block);
+		if (unlikely(err))
+			goto out_free;
+
+		/* Go low */
+		block = block->left;
+		i--;
+	}
+
+	mark_allocated(block);
+	return block;
+
+out_free:
+	__i915_buddy_free(mm, block);
+	return ERR_PTR(err);
+}
+
+static inline bool overlaps(u64 s1, u64 e1, u64 s2, u64 e2)
+{
+	return s1 <= e2 && e1 >= s2;
+}
+
+static inline bool contains(u64 s1, u64 e1, u64 s2, u64 e2)
+{
+	return s1 <= s2 && e1 >= e2;
+}
+
+/*
+ * Allocate range. Note that it's safe to chain together multiple alloc_ranges
+ * with the same blocks list.
+ *
+ * Intended for pre-allocating portions of the address space, for example to
+ * reserve a block for the initial framebuffer or similar, hence the expectation
+ * here is that i915_buddy_alloc() is still the main vehicle for
+ * allocations, so if that's not the case then the drm_mm range allocator is
+ * probably a much better fit, and so you should probably go use that instead.
+ */
+int i915_buddy_alloc_range(struct i915_buddy_mm *mm,
+			   struct list_head *blocks,
+			   u64 start, u64 size)
+{
+	struct i915_buddy_block *block;
+	struct i915_buddy_block *buddy;
+	LIST_HEAD(allocated);
+	LIST_HEAD(dfs);
+	u64 end;
+	int err;
+	int i;
+
+	if (size < mm->chunk_size)
+		return -EINVAL;
+
+	if (!IS_ALIGNED(size | start, mm->chunk_size))
+		return -EINVAL;
+
+	if (range_overflows(start, size, mm->size))
+		return -EINVAL;
+
+	for (i = 0; i < mm->n_roots; ++i)
+		list_add_tail(&mm->roots[i]->tmp_link, &dfs);
+
+	end = start + size - 1;
+
+	do {
+		u64 block_start;
+		u64 block_end;
+
+		block = list_first_entry_or_null(&dfs,
+						 struct i915_buddy_block,
+						 tmp_link);
+		if (!block)
+			break;
+
+		list_del(&block->tmp_link);
+
+		block_start = i915_buddy_block_offset(block);
+		block_end = block_start + i915_buddy_block_size(mm, block) - 1;
+
+		if (!overlaps(start, end, block_start, block_end))
+			continue;
+
+		if (i915_buddy_block_is_allocated(block)) {
+			err = -ENOSPC;
+			goto err_free;
+		}
+
+		if (contains(start, end, block_start, block_end)) {
+			if (!i915_buddy_block_is_free(block)) {
+				err = -ENOSPC;
+				goto err_free;
+			}
+
+			mark_allocated(block);
+			list_add_tail(&block->link, &allocated);
+			continue;
+		}
+
+		if (!i915_buddy_block_is_split(block)) {
+			err = split_block(mm, block);
+			if (unlikely(err))
+				goto err_undo;
+		}
+
+		list_add(&block->right->tmp_link, &dfs);
+		list_add(&block->left->tmp_link, &dfs);
+	} while (1);
+
+	list_splice_tail(&allocated, blocks);
+	return 0;
+
+err_undo:
+	/*
+	 * We really don't want to leave around a bunch of split blocks, since
+	 * bigger is better, so make sure we merge everything back before we
+	 * free the allocated blocks.
+	 */
+	buddy = get_buddy(block);
+	if (buddy &&
+	    (i915_buddy_block_is_free(block) &&
+	     i915_buddy_block_is_free(buddy)))
+		__i915_buddy_free(mm, block);
+
+err_free:
+	i915_buddy_free_list(mm, &allocated);
+	return err;
+}
+
+#if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
+#include "selftests/i915_buddy.c"
+#endif
diff --git a/drivers/gpu/drm/i915/i915_buddy.h b/drivers/gpu/drm/i915/i915_buddy.h
new file mode 100644
index 000000000000..ed41f3507cdc
--- /dev/null
+++ b/drivers/gpu/drm/i915/i915_buddy.h
@@ -0,0 +1,128 @@
+/* SPDX-License-Identifier: MIT */
+/*
+ * Copyright © 2019 Intel Corporation
+ */
+
+#ifndef __I915_BUDDY_H__
+#define __I915_BUDDY_H__
+
+#include <linux/bitops.h>
+#include <linux/list.h>
+
+struct i915_buddy_block {
+#define I915_BUDDY_HEADER_OFFSET GENMASK_ULL(63, 12)
+#define I915_BUDDY_HEADER_STATE  GENMASK_ULL(11, 10)
+#define   I915_BUDDY_ALLOCATED	   (1 << 10)
+#define   I915_BUDDY_FREE	   (2 << 10)
+#define   I915_BUDDY_SPLIT	   (3 << 10)
+#define I915_BUDDY_HEADER_ORDER  GENMASK_ULL(9, 0)
+	u64 header;
+
+	struct i915_buddy_block *left;
+	struct i915_buddy_block *right;
+	struct i915_buddy_block *parent;
+
+	void *private; /* owned by creator */
+
+	/*
+	 * While the block is allocated by the user through i915_buddy_alloc*,
+	 * the user has ownership of the link, for example to maintain within
+	 * a list, if so desired. As soon as the block is freed with
+	 * i915_buddy_free* ownership is given back to the mm.
+	 */
+	struct list_head link;
+	struct list_head tmp_link;
+};
+
+#define I915_BUDDY_MAX_ORDER  I915_BUDDY_HEADER_ORDER
+
+/*
+ * Binary Buddy System.
+ *
+ * Locking should be handled by the user, a simple mutex around
+ * i915_buddy_alloc* and i915_buddy_free* should suffice.
+ */
+struct i915_buddy_mm {
+	/* Maintain a free list for each order. */
+	struct list_head *free_list;
+
+	/*
+	 * Maintain explicit binary tree(s) to track the allocation of the
+	 * address space. This gives us a simple way of finding a buddy block
+	 * and performing the potentially recursive merge step when freeing a
+	 * block.  Nodes are either allocated or free, in which case they will
+	 * also exist on the respective free list.
+	 */
+	struct i915_buddy_block **roots;
+
+	/*
+	 * Anything from here is public, and remains static for the lifetime of
+	 * the mm. Everything above is considered do-not-touch.
+	 */
+	unsigned int n_roots;
+	unsigned int max_order;
+
+	/* Must be at least PAGE_SIZE */
+	u64 chunk_size;
+	u64 size;
+};
+
+static inline u64
+i915_buddy_block_offset(struct i915_buddy_block *block)
+{
+	return block->header & I915_BUDDY_HEADER_OFFSET;
+}
+
+static inline unsigned int
+i915_buddy_block_order(struct i915_buddy_block *block)
+{
+	return block->header & I915_BUDDY_HEADER_ORDER;
+}
+
+static inline unsigned int
+i915_buddy_block_state(struct i915_buddy_block *block)
+{
+	return block->header & I915_BUDDY_HEADER_STATE;
+}
+
+static inline bool
+i915_buddy_block_is_allocated(struct i915_buddy_block *block)
+{
+	return i915_buddy_block_state(block) == I915_BUDDY_ALLOCATED;
+}
+
+static inline bool
+i915_buddy_block_is_free(struct i915_buddy_block *block)
+{
+	return i915_buddy_block_state(block) == I915_BUDDY_FREE;
+}
+
+static inline bool
+i915_buddy_block_is_split(struct i915_buddy_block *block)
+{
+	return i915_buddy_block_state(block) == I915_BUDDY_SPLIT;
+}
+
+static inline u64
+i915_buddy_block_size(struct i915_buddy_mm *mm,
+		      struct i915_buddy_block *block)
+{
+	return mm->chunk_size << i915_buddy_block_order(block);
+}
+
+int i915_buddy_init(struct i915_buddy_mm *mm, u64 size, u64 chunk_size);
+
+void i915_buddy_fini(struct i915_buddy_mm *mm);
+
+struct i915_buddy_block *
+i915_buddy_alloc(struct i915_buddy_mm *mm, unsigned int order);
+
+int i915_buddy_alloc_range(struct i915_buddy_mm *mm,
+			   struct list_head *blocks,
+			   u64 start, u64 size);
+
+void i915_buddy_free(struct i915_buddy_mm *mm, struct i915_buddy_block *block);
+
+void i915_buddy_free_list(struct i915_buddy_mm *mm, struct list_head *objects);
+
+#endif
diff --git a/drivers/gpu/drm/i915/i915_globals.c b/drivers/gpu/drm/i915/i915_globals.c
index 2d5fcba98841..be127cd28931 100644
--- a/drivers/gpu/drm/i915/i915_globals.c
+++ b/drivers/gpu/drm/i915/i915_globals.c
@@ -62,6 +62,7 @@ static void __i915_globals_cleanup(void)
 
 static __initconst int (* const initfn[])(void) = {
 	i915_global_active_init,
+	i915_global_buddy_init,
 	i915_global_context_init,
 	i915_global_gem_context_init,
 	i915_global_objects_init,
diff --git a/drivers/gpu/drm/i915/i915_globals.h b/drivers/gpu/drm/i915/i915_globals.h
index 2d199f411a4a..b2f5cd9b9b1a 100644
--- a/drivers/gpu/drm/i915/i915_globals.h
+++ b/drivers/gpu/drm/i915/i915_globals.h
@@ -27,6 +27,7 @@ void i915_globals_exit(void);
 
 /* constructors */
 int i915_global_active_init(void);
+int i915_global_buddy_init(void);
 int i915_global_context_init(void);
 int i915_global_gem_context_init(void);
 int i915_global_objects_init(void);
diff --git a/drivers/gpu/drm/i915/selftests/i915_buddy.c b/drivers/gpu/drm/i915/selftests/i915_buddy.c
new file mode 100644
index 000000000000..b839dd99dd1f
--- /dev/null
+++ b/drivers/gpu/drm/i915/selftests/i915_buddy.c
@@ -0,0 +1,719 @@
+// SPDX-License-Identifier: MIT
+/*
+ * Copyright © 2019 Intel Corporation
+ */
+
+#include <linux/prime_numbers.h>
+
+#include "../i915_selftest.h"
+#include "i915_random.h"
+
+#define SZ_8G (1ULL << 33)
+
+static void __igt_dump_block(struct i915_buddy_mm *mm,
+			     struct i915_buddy_block *block,
+			     bool buddy)
+{
+	pr_err("block info: header=%llx, state=%u, order=%d, offset=%llx size=%llx root=%s buddy=%s\n",
+	       block->header,
+	       i915_buddy_block_state(block),
+	       i915_buddy_block_order(block),
+	       i915_buddy_block_offset(block),
+	       i915_buddy_block_size(mm, block),
+	       yesno(!block->parent),
+	       yesno(buddy));
+}
+
+static void igt_dump_block(struct i915_buddy_mm *mm,
+			   struct i915_buddy_block *block)
+{
+	struct i915_buddy_block *buddy;
+
+	__igt_dump_block(mm, block, false);
+
+	buddy = get_buddy(block);
+	if (buddy)
+		__igt_dump_block(mm, buddy, true);
+}
+
+static int igt_check_block(struct i915_buddy_mm *mm,
+			   struct i915_buddy_block *block)
+{
+	struct i915_buddy_block *buddy;
+	unsigned int block_state;
+	u64 block_size;
+	u64 offset;
+	int err = 0;
+
+	block_state = i915_buddy_block_state(block);
+
+	if (block_state != I915_BUDDY_ALLOCATED &&
+	    block_state != I915_BUDDY_FREE &&
+	    block_state != I915_BUDDY_SPLIT) {
+		pr_err("block state mismatch\n");
+		err = -EINVAL;
+	}
+
+	block_size = i915_buddy_block_size(mm, block);
+	offset = i915_buddy_block_offset(block);
+
+	if (block_size < mm->chunk_size) {
+		pr_err("block size smaller than min size\n");
+		err = -EINVAL;
+	}
+
+	if (!is_power_of_2(block_size)) {
+		pr_err("block size not power of two\n");
+		err = -EINVAL;
+	}
+
+	if (!IS_ALIGNED(block_size, mm->chunk_size)) {
+		pr_err("block size not aligned to min size\n");
+		err = -EINVAL;
+	}
+
+	if (!IS_ALIGNED(offset, mm->chunk_size)) {
+		pr_err("block offset not aligned to min size\n");
+		err = -EINVAL;
+	}
+
+	if (!IS_ALIGNED(offset, block_size)) {
+		pr_err("block offset not aligned to block size\n");
+		err = -EINVAL;
+	}
+
+	buddy = get_buddy(block);
+
+	if (!buddy && block->parent) {
+		pr_err("buddy has gone fishing\n");
+		err = -EINVAL;
+	}
+
+	if (buddy) {
+		if (i915_buddy_block_offset(buddy) != (offset ^ block_size)) {
+			pr_err("buddy has wrong offset\n");
+			err = -EINVAL;
+		}
+
+		if (i915_buddy_block_size(mm, buddy) != block_size) {
+			pr_err("buddy size mismatch\n");
+			err = -EINVAL;
+		}
+
+		if (i915_buddy_block_state(buddy) == block_state &&
+		    block_state == I915_BUDDY_FREE) {
+			pr_err("block and its buddy are free\n");
+			err = -EINVAL;
+		}
+	}
+
+	return err;
+}
+
+static int igt_check_blocks(struct i915_buddy_mm *mm,
+			    struct list_head *blocks,
+			    u64 expected_size,
+			    bool is_contiguous)
+{
+	struct i915_buddy_block *block;
+	struct i915_buddy_block *prev;
+	u64 total;
+	int err = 0;
+
+	block = NULL;
+	prev = NULL;
+	total = 0;
+
+	list_for_each_entry(block, blocks, link) {
+		err = igt_check_block(mm, block);
+
+		if (!i915_buddy_block_is_allocated(block)) {
+			pr_err("block not allocated\n"),
+			err = -EINVAL;
+		}
+
+		if (is_contiguous && prev) {
+			u64 prev_block_size;
+			u64 prev_offset;
+			u64 offset;
+
+			prev_offset = i915_buddy_block_offset(prev);
+			prev_block_size = i915_buddy_block_size(mm, prev);
+			offset = i915_buddy_block_offset(block);
+
+			if (offset != (prev_offset + prev_block_size)) {
+				pr_err("block offset mismatch\n");
+				err = -EINVAL;
+			}
+		}
+
+		if (err)
+			break;
+
+		total += i915_buddy_block_size(mm, block);
+		prev = block;
+	}
+
+	if (!err) {
+		if (total != expected_size) {
+			pr_err("size mismatch, expected=%llx, found=%llx\n",
+			       expected_size, total);
+			err = -EINVAL;
+		}
+		return err;
+	}
+
+	if (prev) {
+		pr_err("prev block, dump:\n");
+		igt_dump_block(mm, prev);
+	}
+
+	if (block) {
+		pr_err("bad block, dump:\n");
+		igt_dump_block(mm, block);
+	}
+
+	return err;
+}
+
+static int igt_check_mm(struct i915_buddy_mm *mm)
+{
+	struct i915_buddy_block *root;
+	struct i915_buddy_block *prev;
+	unsigned int i;
+	u64 total;
+	int err = 0;
+
+	if (!mm->n_roots) {
+		pr_err("n_roots is zero\n");
+		return -EINVAL;
+	}
+
+	if (mm->n_roots != hweight64(mm->size)) {
+		pr_err("n_roots mismatch, n_roots=%u, expected=%lu\n",
+		       mm->n_roots, hweight64(mm->size));
+		return -EINVAL;
+	}
+
+	root = NULL;
+	prev = NULL;
+	total = 0;
+
+	for (i = 0; i < mm->n_roots; ++i) {
+		struct i915_buddy_block *block;
+		unsigned int order;
+
+		root = mm->roots[i];
+		if (!root) {
+			pr_err("root(%u) is NULL\n", i);
+			err = -EINVAL;
+			break;
+		}
+
+		err = igt_check_block(mm, root);
+
+		if (!i915_buddy_block_is_free(root)) {
+			pr_err("root not free\n");
+			err = -EINVAL;
+		}
+
+		order = i915_buddy_block_order(root);
+
+		if (!i) {
+			if (order != mm->max_order) {
+				pr_err("max order root missing\n");
+				err = -EINVAL;
+			}
+		}
+
+		if (prev) {
+			u64 prev_block_size;
+			u64 prev_offset;
+			u64 offset;
+
+			prev_offset = i915_buddy_block_offset(prev);
+			prev_block_size = i915_buddy_block_size(mm, prev);
+			offset = i915_buddy_block_offset(root);
+
+			if (offset != (prev_offset + prev_block_size)) {
+				pr_err("root offset mismatch\n");
+				err = -EINVAL;
+			}
+		}
+
+		block = list_first_entry_or_null(&mm->free_list[order],
+						 struct i915_buddy_block,
+						 link);
+		if (block != root) {
+			pr_err("root mismatch at order=%u\n", order);
+			err = -EINVAL;
+		}
+
+		if (err)
+			break;
+
+		prev = root;
+		total += i915_buddy_block_size(mm, root);
+	}
+
+	if (!err) {
+		if (total != mm->size) {
+			pr_err("expected mm size=%llx, found=%llx\n", mm->size,
+			       total);
+			err = -EINVAL;
+		}
+		return err;
+	}
+
+	if (prev) {
+		pr_err("prev root(%u), dump:\n", i - 1);
+		igt_dump_block(mm, prev);
+	}
+
+	if (root) {
+		pr_err("bad root(%u), dump:\n", i);
+		igt_dump_block(mm, root);
+	}
+
+	return err;
+}
+
+static void igt_mm_config(u64 *size, u64 *chunk_size)
+{
+	I915_RND_STATE(prng);
+	u64 s, ms;
+
+	/* Nothing fancy, just try to get an interesting bit pattern */
+
+	prandom_seed_state(&prng, i915_selftest.random_seed);
+
+	s = i915_prandom_u64_state(&prng) & (SZ_8G - 1);
+	ms = BIT_ULL(12 + (prandom_u32_state(&prng) % ilog2(s >> 12)));
+	s = max(s & -ms, ms);
+
+	*chunk_size = ms;
+	*size = s;
+}
+
+static int igt_buddy_alloc_smoke(void *arg)
+{
+	struct i915_buddy_mm mm;
+	int max_order;
+	u64 chunk_size;
+	u64 mm_size;
+	int err;
+
+	igt_mm_config(&mm_size, &chunk_size);
+
+	pr_info("buddy_init with size=%llx, chunk_size=%llx\n", mm_size, chunk_size);
+
+	err = i915_buddy_init(&mm, mm_size, chunk_size);
+	if (err) {
+		pr_err("buddy_init failed(%d)\n", err);
+		return err;
+	}
+
+	for (max_order = mm.max_order; max_order >= 0; max_order--) {
+		struct i915_buddy_block *block;
+		int order;
+		LIST_HEAD(blocks);
+		u64 total;
+
+		err = igt_check_mm(&mm);
+		if (err) {
+			pr_err("pre-mm check failed, abort\n");
+			break;
+		}
+
+		pr_info("filling from max_order=%u\n", max_order);
+
+		order = max_order;
+		total = 0;
+
+		do {
+retry:
+			block = i915_buddy_alloc(&mm, order);
+			if (IS_ERR(block)) {
+				err = PTR_ERR(block);
+				if (err == -ENOMEM) {
+					pr_info("buddy_alloc hit -ENOMEM with order=%d\n",
+						order);
+				} else {
+					if (order--) {
+						err = 0;
+						goto retry;
+					}
+
+					pr_err("buddy_alloc with order=%d failed(%d)\n",
+					       order, err);
+				}
+
+				break;
+			}
+
+			list_add_tail(&block->link, &blocks);
+
+			if (i915_buddy_block_order(block) != order) {
+				pr_err("buddy_alloc order mismatch\n");
+				err = -EINVAL;
+				break;
+			}
+
+			total += i915_buddy_block_size(&mm, block);
+		} while (total < mm.size);
+
+		if (!err)
+			err = igt_check_blocks(&mm, &blocks, total, false);
+
+		i915_buddy_free_list(&mm, &blocks);
+
+		if (!err) {
+			err = igt_check_mm(&mm);
+			if (err)
+				pr_err("post-mm check failed\n");
+		}
+
+		if (err)
+			break;
+	}
+
+	if (err == -ENOMEM)
+		err = 0;
+
+	i915_buddy_fini(&mm);
+
+	return err;
+}
+
+static int igt_buddy_alloc_pessimistic(void *arg)
+{
+	const unsigned int max_order = 16;
+	struct i915_buddy_block *block, *bn;
+	struct i915_buddy_mm mm;
+	unsigned int order;
+	LIST_HEAD(blocks);
+	int err;
+
+	/*
+	 * Create a pot-sized mm, then allocate one of each possible
+	 * order within. This should leave the mm with exactly one
+	 * page left.
+	 */
+
+	err = i915_buddy_init(&mm, PAGE_SIZE << max_order, PAGE_SIZE);
+	if (err) {
+		pr_err("buddy_init failed(%d)\n", err);
+		return err;
+	}
+	GEM_BUG_ON(mm.max_order != max_order);
+
+	for (order = 0; order < max_order; order++) {
+		block = i915_buddy_alloc(&mm, order);
+		if (IS_ERR(block)) {
+			pr_info("buddy_alloc hit -ENOMEM with order=%d\n",
+				order);
+			err = PTR_ERR(block);
+			goto err;
+		}
+
+		list_add_tail(&block->link, &blocks);
+	}
+
+	/* And now the last remaining block available */
+	block = i915_buddy_alloc(&mm, 0);
+	if (IS_ERR(block)) {
+		pr_info("buddy_alloc hit -ENOMEM on final alloc\n");
+		err = PTR_ERR(block);
+		goto err;
+	}
+	list_add_tail(&block->link, &blocks);
+
+	/* Should be completely full! */
+	for (order = max_order; order--; ) {
+		block = i915_buddy_alloc(&mm, order);
+		if (!IS_ERR(block)) {
+			pr_info("buddy_alloc unexpectedly succeeded at order %d, it should be full!",
+				order);
+			list_add_tail(&block->link, &blocks);
+			err = -EINVAL;
+			goto err;
+		}
+	}
+
+	block = list_last_entry(&blocks, typeof(*block), link);
+	list_del(&block->link);
+	i915_buddy_free(&mm, block);
+
+	/* As we free in increasing size, we make available larger blocks */
+	order = 1;
+	list_for_each_entry_safe(block, bn, &blocks, link) {
+		list_del(&block->link);
+		i915_buddy_free(&mm, block);
+
+		block = i915_buddy_alloc(&mm, order);
+		if (IS_ERR(block)) {
+			pr_info("buddy_alloc (realloc) hit -ENOMEM with order=%d\n",
+				order);
+			err = PTR_ERR(block);
+			goto err;
+		}
+		i915_buddy_free(&mm, block);
+		order++;
+	}
+
+	/* To confirm, now the whole mm should be available */
+	block = i915_buddy_alloc(&mm, max_order);
+	if (IS_ERR(block)) {
+		pr_info("buddy_alloc (realloc) hit -ENOMEM with order=%d\n",
+			max_order);
+		err = PTR_ERR(block);
+		goto err;
+	}
+	i915_buddy_free(&mm, block);
+
+err:
+	i915_buddy_free_list(&mm, &blocks);
+	i915_buddy_fini(&mm);
+	return err;
+}
+
+static int igt_buddy_alloc_optimistic(void *arg)
+{
+	const int max_order = 16;
+	struct i915_buddy_block *block;
+	struct i915_buddy_mm mm;
+	LIST_HEAD(blocks);
+	int order;
+	int err;
+
+	/*
+	 * Create a mm with one block of each order available, and
+	 * try to allocate them all.
+	 */
+
+	err = i915_buddy_init(&mm,
+			      PAGE_SIZE * ((1 << (max_order + 1)) - 1),
+			      PAGE_SIZE);
+	if (err) {
+		pr_err("buddy_init failed(%d)\n", err);
+		return err;
+	}
+	GEM_BUG_ON(mm.max_order != max_order);
+
+	for (order = 0; order <= max_order; order++) {
+		block = i915_buddy_alloc(&mm, order);
+		if (IS_ERR(block)) {
+			pr_info("buddy_alloc hit -ENOMEM with order=%d\n",
+				order);
+			err = PTR_ERR(block);
+			goto err;
+		}
+
+		list_add_tail(&block->link, &blocks);
+	}
+
+	/* Should be completely full! */
+	block = i915_buddy_alloc(&mm, 0);
+	if (!IS_ERR(block)) {
+		pr_info("buddy_alloc unexpectedly succeeded, it should be full!");
+		list_add_tail(&block->link, &blocks);
+		err = -EINVAL;
+		goto err;
+	}
+
+err:
+	i915_buddy_free_list(&mm, &blocks);
+	i915_buddy_fini(&mm);
+	return err;
+}
+
+static int igt_buddy_alloc_pathological(void *arg)
+{
+	const int max_order = 16;
+	struct i915_buddy_block *block;
+	struct i915_buddy_mm mm;
+	LIST_HEAD(blocks);
+	LIST_HEAD(holes);
+	int order, top;
+	int err;
+
+	/*
+	 * Create a pot-sized mm, then allocate one of each possible
+	 * order within. This should leave the mm with exactly one
+	 * page left. Free the largest block, then whittle down again.
+	 * Eventually we will have a fully 50% fragmented mm.
+	 */
+
+	err = i915_buddy_init(&mm, PAGE_SIZE << max_order, PAGE_SIZE);
+	if (err) {
+		pr_err("buddy_init failed(%d)\n", err);
+		return err;
+	}
+	GEM_BUG_ON(mm.max_order != max_order);
+
+	for (top = max_order; top; top--) {
+		/* Make room by freeing the largest allocated block */
+		block = list_first_entry_or_null(&blocks, typeof(*block), link);
+		if (block) {
+			list_del(&block->link);
+			i915_buddy_free(&mm, block);
+		}
+
+		for (order = top; order--; ) {
+			block = i915_buddy_alloc(&mm, order);
+			if (IS_ERR(block)) {
+				pr_info("buddy_alloc hit -ENOMEM with order=%d, top=%d\n",
+					order, top);
+				err = PTR_ERR(block);
+				goto err;
+			}
+			list_add_tail(&block->link, &blocks);
+		}
+
+		/* There should be one final page for this sub-allocation */
+		block = i915_buddy_alloc(&mm, 0);
+		if (IS_ERR(block)) {
+			pr_info("buddy_alloc hit -ENOMEM for hole\n");
+			err = PTR_ERR(block);
+			goto err;
+		}
+		list_add_tail(&block->link, &holes);
+
+		block = i915_buddy_alloc(&mm, top);
+		if (!IS_ERR(block)) {
+			pr_info("buddy_alloc unexpectedly succeeded at top-order %d/%d, it should be full!",
+				top, max_order);
+			list_add_tail(&block->link, &blocks);
+			err = -EINVAL;
+			goto err;
+		}
+	}
+
+	i915_buddy_free_list(&mm, &holes);
+
+	/* Nothing larger than blocks of chunk_size now available */
+	for (order = 1; order <= max_order; order++) {
+		block = i915_buddy_alloc(&mm, order);
+		if (!IS_ERR(block)) {
+			pr_info("buddy_alloc unexpectedly succeeded at order %d, it should be full!",
+				order);
+			list_add_tail(&block->link, &blocks);
+			err = -EINVAL;
+			goto err;
+		}
+	}
+
+err:
+	list_splice_tail(&holes, &blocks);
+	i915_buddy_free_list(&mm, &blocks);
+	i915_buddy_fini(&mm);
+	return err;
+}
+
+static int igt_buddy_alloc_range(void *arg)
+{
+	struct i915_buddy_mm mm;
+	unsigned long page_num;
+	LIST_HEAD(blocks);
+	u64 chunk_size;
+	u64 offset;
+	u64 size;
+	u64 rem;
+	int err;
+
+	igt_mm_config(&size, &chunk_size);
+
+	pr_info("buddy_init with size=%llx, chunk_size=%llx\n", size, chunk_size);
+
+	err = i915_buddy_init(&mm, size, chunk_size);
+	if (err) {
+		pr_err("buddy_init failed(%d)\n", err);
+		return err;
+	}
+
+	err = igt_check_mm(&mm);
+	if (err) {
+		pr_err("pre-mm check failed, abort, abort, abort!\n");
+		goto err_fini;
+	}
+
+	rem = mm.size;
+	offset = 0;
+
+	for_each_prime_number_from(page_num, 1, ULONG_MAX - 1) {
+		struct i915_buddy_block *block;
+		LIST_HEAD(tmp);
+
+		size = min(page_num * mm.chunk_size, rem);
+
+		err = i915_buddy_alloc_range(&mm, &tmp, offset, size);
+		if (err) {
+			if (err == -ENOMEM) {
+				pr_info("alloc_range hit -ENOMEM with size=%llx\n",
+					size);
+			} else {
+				pr_err("alloc_range with offset=%llx, size=%llx failed(%d)\n",
+				       offset, size, err);
+			}
+
+			break;
+		}
+
+		block = list_first_entry_or_null(&tmp,
+						 struct i915_buddy_block,
+						 link);
+		if (!block) {
+			pr_err("alloc_range has no blocks\n");
+			err = -EINVAL;
+		}
+
+		if (i915_buddy_block_offset(block) != offset) {
+			pr_err("alloc_range start offset mismatch, found=%llx, expected=%llx\n",
+			       i915_buddy_block_offset(block), offset);
+			err = -EINVAL;
+		}
+
+		if (!err)
+			err = igt_check_blocks(&mm, &tmp, size, true);
+
+		list_splice_tail(&tmp, &blocks);
+
+		if (err)
+			break;
+
+		offset += size;
+
+		rem -= size;
+		if (!rem)
+			break;
+	}
+
+	if (err == -ENOMEM)
+		err = 0;
+
+	i915_buddy_free_list(&mm, &blocks);
+
+	if (!err) {
+		err = igt_check_mm(&mm);
+		if (err)
+			pr_err("post-mm check failed\n");
+	}
+
+err_fini:
+	i915_buddy_fini(&mm);
+
+	return err;
+}
+
+int i915_buddy_mock_selftests(void)
+{
+	static const struct i915_subtest tests[] = {
+		SUBTEST(igt_buddy_alloc_pessimistic),
+		SUBTEST(igt_buddy_alloc_optimistic),
+		SUBTEST(igt_buddy_alloc_pathological),
+		SUBTEST(igt_buddy_alloc_smoke),
+		SUBTEST(igt_buddy_alloc_range),
+	};
+
+	return i915_subtests(tests, NULL);
+}
diff --git a/drivers/gpu/drm/i915/selftests/i915_mock_selftests.h b/drivers/gpu/drm/i915/selftests/i915_mock_selftests.h
index b55da4d9ccba..b88084fe3269 100644
--- a/drivers/gpu/drm/i915/selftests/i915_mock_selftests.h
+++ b/drivers/gpu/drm/i915/selftests/i915_mock_selftests.h
@@ -25,3 +25,4 @@ selftest(evict, i915_gem_evict_mock_selftests)
 selftest(gtt, i915_gem_gtt_mock_selftests)
 selftest(hugepages, i915_gem_huge_page_mock_selftests)
 selftest(contexts, i915_gem_context_mock_selftests)
+selftest(buddy, i915_buddy_mock_selftests)